Tunnel freezers are well known in the art. The conventional tunnel freezer comprises:
(a) an elongated tunnel having a first end and a second end; PA1 (b) an item entrance port located at or near the first end for introducing items to be frozen into the tunnel; PA1 (c) an item exit port located at or near the second end for withdrawing the frozen items from the tunnel; PA1 (d) a conveyor belt for moving the items from the item entrance port, through the tunnel, and to the item exit port; PA1 (e) a refrigerant admission port for introducing a refrigerant into the tunnel; and PA1 (f) a refrigerant discharge port for withdrawing the refrigerant from the tunnel.
See for example U.S. Pat. No. 4,800,728 by Klee.
There is a need in the food freezing industry to crust freeze the bottom surfaces of items to be processed without substantially refrigerating the remainder of the items. In this manner, the item is made ready to transfer for downstream operations without worry of sticking to belt surfaces. An example of such an operation is caramel coated cookies or peanut brittle candies where subsequent transfer to other operations needs to be accomplished. Without setting the bottom surface via cryogenic freezing, the item can be torn or ripped in transfer.
The drum freezer taught in U.S. Pat. No. 4,914,927 by Miller et al. can crust freeze bottom surfaces without substantially refrigerating the remainder of the item but unfortunately adds an undesirable curvature to the item due to the item being placed on the circumference. The present invention overcomes this deficiency in the prior art drum freezer.